The statements in this section merely provide background information related to the present disclosure. Accordingly, such statements are not intended to constitute an admission of prior art.
Vehicle systems include powertrain systems that provide tractive torque for propulsion. Powertrain systems may include hybrid electric systems, all-electric systems, and extended-range electric systems that may be configured to operate in various operating modes to generate and transfer torque to a driveline. Such powertrain systems use torque-generative devices, clutches and transmissions. Torque-generative devices include internal combustion engines and electrically-powered machines (often referred to as electric motors or generators).
Known powertrain systems employ control schemes to minimize fuel consumption in an internal combustion engine while responding to operator torque requests for tractive power.
Consumed fuel generates power and heat, which may be used elsewhere in the powertrain system and vehicle, such as in a vehicle cabin compartment. Known vehicle systems include that make use of the power and/or heat can include, but are not limited to, operator-controllable heating, ventilating, and air conditioning (HVAC) systems. These systems can include a controllable electric-powered cabin heater, a controllable electric-powered windshield defogger, a controllable electric-powered rear window defogger, etc. Modern automotive HVAC systems have many sensors and control actuators can have, for example, a temperature sensor inside the cabin, one measuring ambient temperature outside and others measuring various temperatures of the system internal workings. The occupant may have some input to the system via a set point or other adjustment. Additional sensors measuring sun heating load, humidity, etc. might be available to the system. The set of actuators might include a variable speed blower, some means for varying air temperature, ducting and doors to control the direction of air flow and the ratio of fresh to recirculated air.
Under certain operating conditions, a powertrain system of a hybrid electric vehicle (HEV) may operate only to minimize fuel consumption may not operate an internal combustion engine in a manner that generates heat to meet thermal demands and requirements, for example for cabin comfort and window defrosting/defogging. When a HEV operates with its internal combustion engine off, this is sometimes referred to in the art as “engine off operating mode.” As such, the waste heat from the internal combustion engine that is typically used to heat the cabin of the vehicle (e.g., when operating colder ambient temperatures) has become more difficult to obtain when a HEV is operating in this engine off operating mode.
Techniques have been developed for controlling a hybrid powertrain system that includes an internal combustion engine. To provide adequate heat to the cabin, heater performance control software can be used to control engine coolant temperature. For example, when the HEV is operating in cold ambient temperatures, the heater performance control logic forces the internal combustion engine on (in situations where the internal combustion engine would normally be off) so that adequate heat can be provided to a heater core to produce vent discharge temperatures into the cabin that are desired to sustain cabin comfort.
According to one approach, operation of the hybrid powertrain system can be controlled in response to a preferred minimum coolant temperature warm-up trajectory for the internal combustion engine.
For example, in accordance with one conventional technique, during warm-up, the engine is controlled such that the engine coolant temperature follows a minimum warm-up trajectory (also referred to herein as a preferred minimum coolant temperature warm-up trajectory or simply as an “engine coolant temperature (ECT) warm-up trajectory”). The outside (or ambient) air temperature, vehicle runtime, vehicle soak time and vehicle run time are used as indicators of temperature of the vehicle interior cabin compartment of a subject vehicle, and are used to select a preferred minimum coolant temperature warm-up trajectory. Interpolation schemes can be implemented to determine a preferred minimum coolant temperature warm-up trajectory for outside air temperatures that lie between the outside air temperatures of 20° C., 10° C., 0° C., −10° C. and −20° C.
A closed-loop control of the hybrid powertrain system is executed in response to the preferred minimum coolant temperature warm-up trajectory. The closed-loop control includes directly monitoring the coolant temperature, preferably using a coolant temperature sensor. A difference between the coolant temperature and a preferred minimum coolant temperature corresponding to vehicle runtime is determined by employing the preferred minimum coolant temperature warm-up trajectory. If the preferred minimum coolant temperature warm-up trajectory is not following the desired curve, the internal combustion engine is forced on so that engine heat increases to track the preferred minimum coolant temperature warm-up trajectory.
The preferred minimum coolant temperature warm-up trajectory is designed to meet worst case cabin performance specifications, and takes into account only the ambient air temperature outside the vehicle and run time. During low load situations, such as at low blower speeds, this can result in vent discharge temperatures that are greater than desired. One drawback of this approach is that it results in increased fuel consumption for other drive cycles with a lower cabin heat loads.
There are a variety of reasons that it is desirable to decrease fuel consumption whenever possible. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.